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The substage condenser gathers light from the microscopic lense light resource and concentrates it into a cone the light the illuminates the specimen through uniform intensity over the entire viewfield. It is crucial that the condenser irradiate cone be properly changed to optimize the intensity and angle of irradiate entering the target front lens. Each time an objective is changed, a corresponding adjustment have to be performed on the substage condenser to provide the suitable light cone for the number aperture that the brand-new objective.

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As a result of no optical correction, the Abbe condenser is suited greatly for routine monitoring with missions of modest number aperture and also magnification. The primary benefits of the Abbe condenser room the broad cone that illumination the the condenser is capable of producing and its capability to job-related with long working distance objectives. Most microscopes are offered by the manufacturer v an Abbe condenser as the default and also these condensers are actual workhorses for regimen laboratory use.

The following level the condenser correction is split in between the aplanatic and also achromatic condensers that space corrected specifically for one of two people spherical (aplanatic) or chromatic (achromatic) optical aberrations. Typical examples of this condensers are illustrated in figures 3 (achromatic) and Figure 4 (aplanatic). Achromatic condensers typically contain three to four lens elements and are corrected in 2 wavelengths (red and blue) because that chromatic aberration.


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The highest level that correction for optical aberration is incorporated in the aplanatic-achromatic condenser. This condenser is well corrected because that both chromatic and also spherical aberrations and is the condenser of choice for usage in an important color photomicrography with white light. A usual aplanatic-achromatic condenser is depicted in number 5 (numerical aperture = 1.35). This condenser functions eight internal lens aspects cemented into two doublets and also four single lenses.


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Engravings uncovered on the condenser housing encompass its kind (achromatic, aplanatic, etc.), the numerical aperture, and a graded scale that suggests the approximate adjustment (size) of the aperture diaphragm. As we stated above, condensers with numerical apertures over 0.95 perform best when a autumn of oil is used to their top lens in contact with the undersurface of the specimen slide. This ensures the oblique irradiate rays emanating from the condenser space not reflect from underneath the slide, but are directed into the specimen. In practice, this can come to be tedious and also is not commonly done in program microscopy, however is necessary when working at high resolutions and also for exact photomicrography utilizing high-power (and numerical aperture) objectives.

Another important consideration is the thickness that the microscope slide, i beg your pardon is as critical to the condenser as coverslip thickness is come the objective. Many commercial producers offer slides that variety in thickness between 0.95 and 1.20 mm through the most typical being an extremely close come 1.0 mm. A microscopic lense slide of thickness 1.20 mm is too thick to be used with many high number aperture condensers that often tend to have actually a really short functioning distance. While this go not significantly matter for routine specimen observation, the results have the right to be disastrous with precision photomicrography. Us recommend that microscopic lense slides be preferred that have a thickness of 1.0 ± 0.05 mm, and also that lock be completely cleaned before use.


Condenser irradiate Cones

Study how optical correction influence the size and also shape the condenser irradiate cones.


When the target is changed, for example from a 10X to 20X, the aperture diaphragm of the condenser must also be readjusted to provide a brand-new light cone that matches the numerical aperture the the brand-new objective. This is excellent by transforming the knurled knob top top the condensers illustrated in figures 2-6. There is a tiny yellow arrowhead or table of contents mark situated on this knob that shows the family member size the the aperture when compared to the direct gradation on the condenser housing. Numerous manufacturers will synchronize this gradation to exchange mail to the approximate number aperture that the condenser. For example, if the microscopist has selected a 10X objective of number aperture 0.25, climate the arrow would be inserted next the worth 0.18-0.20 (about 80 percent of the objective numerical aperture) top top the gradation inscribed on the condenser housing.

Often, that is not practical to use a single condenser through an entire range of missions (2X come 100X) due to the broad selection of irradiate cones that must be developed to enhance objective numerical apertures. V low-power objectives in the range 2X come 5X, the illumination cone will have actually a diameter between 6-10 mm, if the high-power objectives (60X come 100X) require a highly concentrated light cone only around 0.2-0.4 mm in diameter. With a solved focal length, it is challenging to attain this wide range of illumination cones through a single condenser.


In practice, this problem can be resolved in numerous ways. For short power objectives (below 10x), it may be essential to unscrew the optimal lens that the condenser in bespeak to to fill the field of view v light. Part condensers are developed with a flip-top top lens to accomplish this more readily, as shown in number 6. Many manufacturers now develop a condenser which flips over totally when provided with low power objectives. Other companies may incorporate assistant correction lenses in the light course for securing proper illumination through objectives less than 10x. When the condenser is used without its height lens, the aperture iris diaphragm is opened vast and the field diaphragm, currently visible in ~ the back of the objective, serves as if it were the aperture diaphragm. Flip-top condensers are manufactured in a variety of configurations with numerical apertures ranging from 0.65 to 1.35. Those condensers that have a numerical aperture value of 0.95 or much less are intended for use v "dry" objectives. However, flip-top condensers that have actually a number aperture higher than 0.95 are intended because that use through oil-immersion objectives and they must have a autumn of oil placed between the bottom of the microscope slide and also the condenser optimal lens when examining an important samples.

In enhancement to the common brightfield condensers discussed above, there room a wide variety of dedicated models suitable to numerous different applications. Table 2 list a number of different condenser configurations and the to plan applications.


Substage Condenser Applications
CONDENSER TYPEBRIGHTFIELDDARKFIELDPHASECONTRASTDICPOLARIZING
Achromat/ AplanatN.A. 1.3⋅<10x~100x>
Achromat Swing-outN.A. 0.90⋅<4x~100x>
Low-PowerN.A. 0.20⋅<1x~10x>
Phase comparison AbbeN.A. 1.25⋅<10x~100x>
Phase contrast AchromatN.A. 0.85⋅<4x~100x>
DIC UniversalAchromat/Aplanat⋅<10x, 100x>⋅<20x, 40x, 100x>
Darkfield, dryN.A. 0.80~0.95⋅<4x~40x>
Darkfield, oilN.A. 1.20~1.43⋅<4x~100x>
Stain-Free AchromatSwing-Out N.A. 0.90⋅<4x~100x>
Table 2

From the data in Table 2, it is apparent that substage condensers have a good deal that interchangeability amongst different applications. For instance, the DIC universal achromat/aplanat condenser is advantageous for brightfield, darkfield, and also phase contrast, in enhancement to the major DIC application. Other condensers have comparable interchangeability. Us will deal with various aspects of individual methods that need modified condensers in our section on Specialized Microscopy Techniques. You re welcome feel cost-free to visit this interesting component of our Website for more specific information around substage condensers.


Contributing Authors

Mortimer Abramowitz - Olympus America, Inc., 2 Corporate facility Drive., Melville, brand-new York, 11747.

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Michael W. Davidson - nationwide High Magnetic ar Laboratory, 1800 eastern Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.